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Jiang S, Chung S, Ahlberg M, Frisk A, Khymyn R, Le QT, Mazraati H, Houshang A, Heinonen O, Åkerman J. Magnetic droplet soliton pairs. Nat Commun 2024; 15:2118. [PMID: 38459046 PMCID: PMC10923811 DOI: 10.1038/s41467-024-46404-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 02/22/2024] [Indexed: 03/10/2024] Open
Abstract
We demonstrate magnetic droplet soliton pairs in all-perpendicular spin-torque nano-oscillators (STNOs), where one droplet resides in the STNO free layer (FL) and the other in the reference layer (RL). Typically, theoretical, numerical, and experimental droplet studies have focused on the FL, with any additional dynamics in the RL entirely ignored. Here we show that there is not only significant magnetodynamics in the RL, but the RL itself can host a droplet driven by, and coexisting with, the FL droplet. Both single droplets and pairs are observed experimentally as stepwise changes and sharp peaks in the dc and differential resistance, respectively. While the single FL droplet is highly stable, the coexistence state exhibits high-power broadband microwave noise. Furthermore, micromagnetic simulations reveal that the pair dynamics display periodic, quasi-periodic, and chaotic signatures controlled by applied field and current. The strongly interacting and closely spaced droplet pair offers a unique platform for fundamental studies of highly non-linear soliton pair dynamics.
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Affiliation(s)
- S Jiang
- School of Microelectronics, South China University of Technology, 511442, Guangzhou, China
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - S Chung
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.
- Department of Physics Education, Korea National University of Education, Cheongju, 28173, Korea.
| | - M Ahlberg
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.
| | - A Frisk
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - R Khymyn
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - Q Tuan Le
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden
| | - H Mazraati
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden
| | - A Houshang
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - O Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
- Seagate Technology, 7801 Computer Ave., Bloomington, MN, 55435, USA
| | - J Åkerman
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden.
- Center for Science and Innovation in Spintronics, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
- Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
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Muralidhar S, Khymyn R, Awad AA, Alemán A, Hanstorp D, Åkerman J. Femtosecond Laser Pulse Driven Caustic Spin Wave Beams. Phys Rev Lett 2021; 126:037204. [PMID: 33543954 DOI: 10.1103/physrevlett.126.037204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 09/22/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
Controlling the directionality of spin waves is a key ingredient in wave-based computing methods such as magnonics. In this Letter, we demonstrate this particular aspect by using an all-optical pointlike source of continuous spin waves based on frequency comb rapid demagnetization. The emitted spin waves contain a range of k vectors and by detuning the applied magnetic field slightly off the ferromagnetic resonance (FMR), we observe X-shaped caustic spin wave patterns at 70° propagation angles as predicted by theory. When the harmonic of the light source approaches the FMR, the caustic pattern gives way to uniaxial spin wave propagation perpendicular to the in-plane component of the applied field. This field-controlled propagation pattern and directionality of optically emitted short-wavelength spin waves provide additional degrees of freedom when designing magnonic devices.
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Affiliation(s)
- S Muralidhar
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - R Khymyn
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - A A Awad
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - A Alemán
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - D Hanstorp
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - J Åkerman
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- Materials and Nano Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden
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Fulara H, Zahedinejad M, Khymyn R, Awad AA, Muralidhar S, Dvornik M, Åkerman J. Spin-orbit torque-driven propagating spin waves. Sci Adv 2019; 5:eaax8467. [PMID: 31799403 PMCID: PMC6868678 DOI: 10.1126/sciadv.aax8467] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/27/2019] [Indexed: 05/24/2023]
Abstract
Spin-orbit torque (SOT) can drive sustained spin wave (SW) auto-oscillations in a class of emerging microwave devices known as spin Hall nano-oscillators (SHNOs), which have highly nonlinear properties governing robust mutual synchronization at frequencies directly amenable to high-speed neuromorphic computing. However, all demonstrations have relied on localized SW modes interacting through dipolar coupling and/or direct exchange. As nanomagnonics requires propagating SWs for data transfer and additional computational functionality can be achieved using SW interference, SOT-driven propagating SWs would be highly advantageous. Here, we demonstrate how perpendicular magnetic anisotropy can raise the frequency of SOT-driven auto-oscillations in magnetic nanoconstrictions well above the SW gap, resulting in the efficient generation of field and current tunable propagating SWs. Our demonstration greatly extends the functionality and design freedom of SHNOs, enabling long-range SOT-driven SW propagation for nanomagnonics, SW logic, and neuromorphic computing, directly compatible with CMOS technology.
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Affiliation(s)
- H. Fulara
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - M. Zahedinejad
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- NanOsc AB, Electrum 229, 164 40 Kista, Sweden
| | - R. Khymyn
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - A. A. Awad
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- NanOsc AB, Electrum 229, 164 40 Kista, Sweden
| | - S. Muralidhar
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - M. Dvornik
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- NanOsc AB, Electrum 229, 164 40 Kista, Sweden
| | - J. Åkerman
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- NanOsc AB, Electrum 229, 164 40 Kista, Sweden
- Material and Nanophysics, School of Engineering Sciences, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden
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Houshang A, Khymyn R, Fulara H, Gangwar A, Haidar M, Etesami SR, Ferreira R, Freitas PP, Dvornik M, Dumas RK, Åkerman J. Spin transfer torque driven higher-order propagating spin waves in nano-contact magnetic tunnel junctions. Nat Commun 2018; 9:4374. [PMID: 30348986 PMCID: PMC6197248 DOI: 10.1038/s41467-018-06589-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 09/12/2018] [Indexed: 11/08/2022] Open
Abstract
Short wavelength exchange-dominated propagating spin waves will enable magnonic devices to operate at higher frequencies and higher data transmission rates. While giant magnetoresistance (GMR)-based magnetic nanocontacts are efficient injectors of propagating spin waves, the generated wavelengths are 2.6 times the nano-contact diameter, and the electrical signal strength remains too weak for applications. Here we demonstrate nano-contact-based spin wave generation in magnetic tunnel junctions and observe large-frequency steps consistent with the hitherto ignored possibility of second- and third-order propagating spin waves with wavelengths of 120 and 74 nm, i.e., much smaller than the 150-nm nanocontact. Mutual synchronization is also observed on all three propagating modes. These higher-order propagating spin waves will enable magnonic devices to operate at much higher frequencies and greatly increase their transmission rates and spin wave propagating lengths, both proportional to the much higher group velocity.
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Affiliation(s)
- A Houshang
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
- NanOsc AB, 164 40, Kista, Sweden
| | - R Khymyn
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - H Fulara
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - A Gangwar
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - M Haidar
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - S R Etesami
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - R Ferreira
- International Iberian Nanotechnology Laboratory, Braga, 4715-330, Portugal
| | - P P Freitas
- International Iberian Nanotechnology Laboratory, Braga, 4715-330, Portugal
| | - M Dvornik
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - R K Dumas
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - J Åkerman
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.
- NanOsc AB, 164 40, Kista, Sweden.
- Material Physics, School of Engineering Sciences, Royal Institute of Technology, Electrum 229, 164 40, Kista, Sweden.
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Tacchi S, Troncoso RE, Ahlberg M, Gubbiotti G, Madami M, Åkerman J, Landeros P. Interfacial Dzyaloshinskii-Moriya Interaction in Pt/CoFeB Films: Effect of the Heavy-Metal Thickness. Phys Rev Lett 2017; 118:147201. [PMID: 28430498 DOI: 10.1103/physrevlett.118.147201] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Indexed: 06/07/2023]
Abstract
We report the observation of a Pt layer thickness dependence on the induced interfacial Dzyaloshinskii-Moriya interaction in ultrathin Pt(d_{Pt})/CoFeB films. Taking advantage of the large spin-orbit coupling of the heavy metal, the interfacial Dzyaloshinskii-Moriya interaction is quantified by Brillouin light scattering measurements of the frequency nonreciprocity of spin waves in the ferromagnet. The magnitude of the induced Dzyaloshinskii-Moriya coupling is found to saturate to a value of 0.45 mJ/m^{2} for Pt thicknesses larger than ∼2 nm. The experimental results are explained by analytical calculations based on the three-site indirect exchange mechanism that predicts a Dzyaloshinskii-Moriya interaction at the interface between a ferromagnetic thin layer and a heavy metal. Our findings open up a way to control and optimize chiral effects in ferromagnetic thin films through the thickness of the heavy-metal layer.
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Affiliation(s)
- S Tacchi
- Istituto Officina dei Materiali del CNR (CNR-IOM), Sede Secondaria di Perugia, c/o Dipartimento di Fisica e Geologia, Università di Perugia, I-06123 Perugia, Italy
| | - R E Troncoso
- Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso, Chile
| | - M Ahlberg
- Department of Physics, University of Gothenburg, SE-41296 Gothenburg, Sweden
| | - G Gubbiotti
- Istituto Officina dei Materiali del CNR (CNR-IOM), Sede Secondaria di Perugia, c/o Dipartimento di Fisica e Geologia, Università di Perugia, I-06123 Perugia, Italy
| | - M Madami
- Dipartimento di Fisica e Geologia, Università di Perugia, I-06123 Perugia, Italy
| | - J Åkerman
- Department of Physics, University of Gothenburg, SE-41296 Gothenburg, Sweden
- Materials and Nano Physics, Royal Institute of Technology (KTH), SE-164 40 Kista, Sweden
| | - P Landeros
- Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso, Chile
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Houshang A, Iacocca E, Dürrenfeld P, Sani SR, Åkerman J, Dumas RK. Spin-wave-beam driven synchronization of nanocontact spin-torque oscillators. Nat Nanotechnol 2016; 11:280-286. [PMID: 26689379 DOI: 10.1038/nnano.2015.280] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 10/26/2015] [Indexed: 06/05/2023]
Abstract
The synchronization of multiple nanocontact spin-torque oscillators (NC-STOs) is mediated by propagating spin waves (SWs). Although it has been shown that the Oersted field generated in the vicinity of the NC can dramatically alter the emission pattern of SWs, its role in the synchronization behaviour of multiple NCs has not been considered so far. Here we investigate the synchronization behaviour in multiple NC-STOs oriented either vertically or horizontally, with respect to the in-plane component of the external field. Synchronization is promoted (impeded) by the Oersted field landscape when the NCs are oriented vertically (horizontally) due to the highly anisotropic SW propagation. Not only is robust synchronization between two oscillators observed for separations larger than 1,000 nm, but synchronization of up to five oscillators, a new record, has been observed in the vertical array geometry. Furthermore, the synchronization can no longer be considered mutual in nature.
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Affiliation(s)
- A Houshang
- Physics Department, University of Gothenburg, Gothenburg 412 96, Sweden
- NanOsc AB, Kista 164 40, Sweden
| | - E Iacocca
- Physics Department, University of Gothenburg, Gothenburg 412 96, Sweden
- NanOsc AB, Kista 164 40, Sweden
| | - P Dürrenfeld
- Physics Department, University of Gothenburg, Gothenburg 412 96, Sweden
| | - S R Sani
- Material Physics, School of ICT, Royal Institute of Technology, Electrum 229, Kista 164 40, Sweden
| | - J Åkerman
- Physics Department, University of Gothenburg, Gothenburg 412 96, Sweden
- NanOsc AB, Kista 164 40, Sweden
- Material Physics, School of ICT, Royal Institute of Technology, Electrum 229, Kista 164 40, Sweden
| | - R K Dumas
- Physics Department, University of Gothenburg, Gothenburg 412 96, Sweden
- NanOsc AB, Kista 164 40, Sweden
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Sbiaa R, Shaw JM, Nembach HT, Al Bahri M, Ranjbar M, Åkerman J, Piramanayagam SN. Ferromagnetic resonance measurements of (Co/Ni/Co/Pt) multilayers with perpendicular magnetic anisotropy. J Phys D Appl Phys 2016; 49:https://doi.org/10.1088/0022-3727/49/42/425002. [PMID: 33100381 PMCID: PMC7580010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Multilayers of [Co/Ni(t)/Co/Pt]×8 with varying Ni thickness were investigated for possible use as a free layer in magnetic tunnel junctions and spintronics devices. The thickness t of the Ni sub-layer was varied from 0.3 nm to 0.9 nm and the resulting magnetic properties were compared with (Co/Ni) and (Co/Pt) multilayers. As determined from magnetic force microscopy, magnetometry and ferromagnetic resonance measurements, all multilayers exhibited perpendicular magnetic anisotropy. Compared with (Co/Pt) multilayers, the sample with t of 0.9 nm showed almost the same anisotropy field of μ 0 H k = 1.15 T but the damping constant was 40% lower. These characteristics make these multilayers attractive for spin torque based magnetoresistive devices with perpendicular anisotropy.
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Affiliation(s)
- R Sbiaa
- Department of Physics, Sultan Qaboos University, PO Box 36, PC 123, Muscat, Oman
| | - J M Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - H T Nembach
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - M Al Bahri
- Department of Physics, Sultan Qaboos University, PO Box 36, PC 123, Muscat, Oman
| | - M Ranjbar
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, SPMS-04-01, 21 Nanyang Link, 637371, Singapore
| | - J Åkerman
- Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden
- Materials and Nanophysics, School of ICT, KTH Royal Institute of Technology, Isafjordsg. 22, 16440 Kista, Sweden
| | - S N Piramanayagam
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, SPMS-04-01, 21 Nanyang Link, 637371, Singapore
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Kamali S, Zha CL, Yoda Y, Åkerman J. Oxidation states and quality of upper interfaces in magnetic tunnel junctions: oxygen effect on crystallization of interfaces. J Phys Condens Matter 2014; 26:026004. [PMID: 24334442 DOI: 10.1088/0953-8984/26/2/026004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this study, we have deposited an 57Fe sensor layer at the upper interface, i.e. the interface between the oxide barrier and the upper electrode in selected magnetic tunnel junctions (MTJs), in order to perform nuclear resonant scattering with the aim of obtaining direct information on the magnetic properties and quality of this interface. This is a unique approach as it makes use of this powerful technique to give information at the atomic level, and specifically from the interface where the sensor layer is deposited. By varying sample tunnel barrier thicknesses and oxidation times in the preparation of this barrier, we have observed that longer oxidation time results in not only an increase of the magnetic hyperfine fields, but also causes an interesting crystallization and smoothing of the interface. We also observed that boron atoms diffuse away from the lower part of the upper FeCoB electrode toward the capping layer. An important observation, which has a crucial effect in tunnel magnetoresistance values, is the absence of any magnetically dead FeO layer at the interface. Another finding is that the deposition of Fe on MgO is much smoother than the deposition of MgO on Fe.
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